Method and apparatus for the hot piercing of metal billets

ABSTRACT

An improvement in the hot piercing of a previously cold drilled metal billet in which the bottom of the piercing press is equipped with a frustoconically bored ring, the aperture of which noticeably exceeds the cross-section of the desired billet bore or the expanding tool. During extrusion in an extrusion press, the section of the billet coming from the lower part of the piercing press is placed in the extrusion press adjacent to the dummy block.

United States Patent Malegue Jan. 23, 1973 [54] METHOD AND APPARATUS FORTHE 2,320,071 5/1943 Frothingham ..72/256 HOT PIERCING OF METAL BILLETS3,580,038 5/1971 Andressian .....72/273 1,802,785 4/1931 Sin er ..72/266i Aime Malegue, Mombard, Frame 3,525,245 8/1970 sall is ..72/273 [73]Assign': Cefllac, Paris; France FOREIGN PATENTS OR APPLICATIONS Filed:Nov- 1970 728,356 11/1942 Germany ..72/266 [21] Appl. No.: 89,608Primary Examiner--Richard J. Herbst I Att0rr'IeyWebb, Burden, Robinson &Webb [30] Foreign Application Priority Data [57] ABSTRACT NOV. 26, 1969France "6940768 An improvement in the hot p g of a previously colddrilled metal billet in which the bottom of the U-S. l e I press i a f ti uy b d [51 I111. Cl. .....B2lC 23/04 ring, the aperture of whichnoticeably exceeds the [58] new of Search "72/253, 256, cross-section ofthe desired billet bore or the expand- 273129/1316- 1316- 47; ing tool.During extrusion in an extrusion press, the 72/343 section of the billetcoming from the lower part of the piercing press is placed in theextrusion press adjacent [56] Refer nces it d to the dummy block.

UNITED STATES P TE 5 Claims, 1 Drawing Figure 3,581,538 6/1971 Asari..72/273 \M I l2 PATENTEDJAN 23 I975 METHOD AND APPARATUS FOR THE HOTPIERCING OF METAL BILLETS This invention is directed to the hot piercingof metal billets and their extrusion into tubes and hollow sections.More particularly, it is directed to an improved method for carrying outthe hot piercing operation also called expansion which consists in hotdeforming to the desired bore .diameter (also called expansion diameter)a billet in which an axial pilot hole has been previously cold drilled.

Presently, this hot piercing is conducted in a vertical piercing press,the container of which is equipped at its lower end with a cylindricallybored ring through which the piercing tool can run with a very slightclearance, see French Pat. No. 1,130,759. In such a process the lowerportion of the metal billet is sheared off at the end of the hotpiercing operation, thus creating a discard or residue.

Where the expansion diameter is small, the weight of the residue issmall and the presently employed process is generally satisfactory.However, when the expansion diameter is relatively large, the metal lossor residue is substantially more noticeable. Moreover, since the insidediameter of the lower cylindrical ring must be accurately selected, itis necessary to have available as many lower ring sizes as there areexpansion diameters.

The present invention avoids these above-identified drawbacks. With myimproved process, the whole of the billet is deformed during theexpansion operation without any shearing and without producing anydiscard or residue, although the lower face of the billet is deformedinto a bulge during hot piercing, the extent of the bulge increasing asthe ratio of expansion diameter to wall thickness increases. The billetis extruded with its bulged face adjacent to the extrusion ram and,therefore, the bulge becomes part of the extrusion discard. Theextrudate is perfectly satisfactory as regards both metallurgicalstructure and geometry. In addition, a single ring can be used for awide range of expansion diameters.

My invention consists in placing at the lower end of the piercing presscontainer a ring having a frustoconical bore, the smaller base of whichis downstream from the larger base. The smaller base has a diameterlargely exceeding the working diameter of the expansion tool. The billetpreviously drilled and heated to deformation temperature is hot expandedand then is inserted into the container of an extrusion press in such amanner that the billet end coming from the lower part of the piercingpress container comes into contact with the dummy block of the extrusionpress. The extrusion takes place in the known manner.

The preferred embodiment of my invention is shown in the single figureof the accompanying drawing which is an axial section of the lower partof a piercing press equipped with a ring: according to the invention andcontaining a billet just expanded according to may im proved method ofhot piercing.

The container 1 of the piercing press is equipped at its lower end withan annular ring 2. The container 1 and the annular ring 2 are supportedby base sections 7 and SM the piercing press in a known manner. Annularring 2 has a frustoconically shaped central bore 9. An expansion tool 3is secured to a spindle 4 which is acted upon by the press to expand orpierce a billet 5.

The outside diameter of the annular ring 2 is slightly smaller than theinside diameter of the container. The larger base 10 of thefrustoconical bore 9 has a diameter preferably exceeding percent of thecontainer diameter. The smaller base 11 which is downstream of thelarger base 10 has a diameter preferably exceeding 50 percent of thecontainer diameter. The inside surface of the ring 2 terminates in atoric surface 12 melting into the larger base 10. The radius R of thetoric surface 12 is at least 3 percent of the container diameter and notsmaller than 5 mm (0.200 inch), see the figure. The total height of thering is advantageously from 70 to mm (2.750 to 4.750 inch).

My improved process works as follows. A previously drilled billet 5which has also been heated to deformation temperature is positioned incontainer 1 of the piercing press. The expansion tool 3 is forcedthrough the drill bore to form the desired expansion or pierced borediameter in the known manner. However, the metal flow of the billetscreate a bulge 6 at the ring end of the container, see the figure. Theextent of this bulge varies depending upon the ratio of the expansiondiameter and the wall thickness of the hot pierced billet. In otherwords, the greater the metal flow the greater the bulge. However, thereis no discard or residue as in the previously known processes. The hotpierced billet is then positioned in an extrusion press so that the endof the billet containing the bulge is adjacent the standard dummy block.After extrusion in the normal manner, the bulge end of the billetbecomes a part of the standarddiscard.

With only one ring as described above, it is possible to expandbillets'to bore diameters ranging from 25 percent to 70 percent of thediameter of the smaller base of the ring bore.

The surface condition of the billet bore thus obtained is perfectlysound along the whole useful length of the billet. Slight cracks may beobserved only in the bulged lower part of the billet but this is removedwith the extrusion discard.

Thus, the process according to the invention, permits the use of thesame ring for an important range of expansion diameters. Tooling is thussimplified and the operations are accelerated, since it is possible tochange the expansion diameter without changing the ring. On the otherhand, any waste of metal is avoided in the hot piercing operation.

EXAMPLE:

In a vertical hydraulic 400 ton piercing press a 226 mm (8.900 inch)container was equipped with a ring according to the invention, theheight of which was 90 mm (3.540 inch), the inside bore of which had alarger base 175 mm (6.900 inch) and a smaller base mm (5.120 inch) indiameter, respectively. This press was fed with carbon steel billetspreviously cold drilled to 20 mm (0.800 inch) and heated to deformationtemperature. The billets were expanded (hot pierced) to bore diametersranging from 50 to 85 mm (2 to 3.350 inch) without any waste of metal.The billets showed bulged lower faces.

These billets were then inserted into a horizontal 3000 ton extrusionpress in which the bulged faces were adjacent to the dummy block andextruded into tubes, the various inside diameters of which ranged from45 to 80 mm (1.770 to 3.150 inch). The tubes showed a very goodconcentricity and a perfect metallurgical quality along their wholelength.

The metal waste during the successive hot operations was limited to theextrusion discard, i.e., to about 2 percent of the initial metal weight.

ICLAIM:

1. In the process for hot piercing metal billets previously cold drilledand heated to deformation temperature in a piercing press including apiercing press container and an expansion tool and subsequentlyextruding the hot pierced metal billets in an extrusion press includingan extrusion press container and a dummy block, the improvementcomprising:

A. equipping the piercing press container at its lower end with anannular ring having a rustoconical bore, the smaller base of the borebeing downstream of the larger base and having a diameter substantiallylarger than the diameter of the expansion tool;

B. hot piercing with an expansion tool the previously cold drilled andheated billet;

C. inserting the hot pierced billet into the extrusion press containerso that the end of the billet positioned in the lower end of thepiercing press container is adjacent the dummy block; and

D. extruding the hot pierced metal billet.

2. The process of claim 1 wherein the previously cold drilled and heatedbillet is hot pierced so that its resultant bore diameter is from 25 topercent of the diameter of the smaller base of the frusto-conical bore.

3. The process of claim 1 wherein the diameter of said smaller base isat least 50 percent of the diameter of the container and the diameter ofthe larger base is at least 70 percent of the container diameter.

4. The process of claim 1 including employing a glass-like lubricant inat least one of the hot piercing step B or the extruding step D.

5. In a piercing press for hot piercing metal billets previously colddrilled and heated to a deformation temperature including a containerhaving an annular ring cooperating with the lower portion thereof and anexpansion tool, the improvement com-prising said annular ring having afrustoconical bore, the smaller base of the frustoconical bore beingdownstream of the larger base and having a diameter substantially largerthan the diameter of the expansion tool, the ring having an insidesurface terminating at its upstream end in a toric surface melting intosaid larger base, said toric surface being generated with a radius of atleast 3 percent of the diameter of the piercing press container.

1. In the process for hot piercing metal billets previously cold drilledand heated to deformation temperature in a piercing press including apiercing press container and an expansion tool and subsequentlyextruding the hot pierced metal billets in an extrusion press includingan extrusion press container and a dummy block, the improvementcomprising: A. equipping the piercing press container at its lower endwith an annular ring having a rustoconical bore, the smaller base of thebore being downstream of the larger base and having a diametersubstantially larger than the diameter of the expansion tool; B. hotpiercing with an expansion tool the previously cold drilled and heatedbillet; C. inserting the hot pierced billet into the extrusion presscontainer so that the end of the billet positioned in the lower end ofthe piercing press container is adjacent the dummy block; and D.extruding the hot pierced metal billet.
 2. The process of claim 1wherein the previously cold drilled and heated billet is hot pierced sothat its resultant bore diameter is from 25 to 70 percent of thediameter of the smaller base of the frusto-conical bore.
 3. The processof claim 1 wherein the diameter of said smaller base is at least 50percent of the diameter of the container and the diameter of the largerbase is at least 70 percent of the container diameter.
 4. The process ofclaim 1 including employing a glass-like lubricant in at least one ofthe hot piercing step B or the extruding step D.
 5. In a piercing pressfor hot piercing metal billets previously cold drilled and heated to adeformation temperature including a container having an annular ringcooperating with the lower portion thereof and an expansion tool, theimprovement com-prising said annular ring having a frustoconical bore,the smaller base of the frustoconical bore being downstream of thelarger base and having a diameter substantially larger than the diameterof the expansion tool, the ring having an inside surface terminating atits upstream end in a toric surface melting into said larger base, saidtoric surface being generated with a radius of at least 3 percent of thediameter of the piercing press container.